In the past, differentiation therapy has been discussed as a small portion of large meetings on cell differentiation. In the last five years we have established a forum where discussion of this subject is done in depth, with both basic and clinical data presented in detail. In view of the recent interest in the conceptual use of differentiation therapy and its current use in clinical trials through-out the world, we believe that there is a need to have an on-going workshop conference which brings together scientists and clinicians with proven scientific interest in the field. We have already established a communications network of 10 working sub-groups, comprised of over 125 participants, all of whom have demonstrated an interest in the induction of differentiation as a possible therapy. Our original concept was that each participant be committed to participate in the meeting for a period of three years. To that end, working sub-groups were established which fit the scientific expertise of the participant and each has continued to work within this framework. Following the Third Conference in Sardinia in 1988, it was decided that these conferences should be an on-going collaboration and subsequently a Fourth Conference was held in Japan in 1990. At the Fourth Conference, sub-group co-chairmen organized and presented the progress of their working sub-groups and all of the participants reported on their recent studies in the field. As was anticipated following the Third Conference, all of the participants continued to communicate on a regular basis, and several important collaborations have developed from this. The abstracts from the Fourth Conference have been published and the reports from the working sub-groups have been distributed. The second volume of "The Status of the Differentiation Therapy of Cancer" is a direct result of this conference and was published by Raven Press in July, 1991. It was determined, based upon the enthusiasm of all participants, that the conference should continue on a regular basis and these participants have committed themselves to continued collaboration for another four years. It is our belief that this structure will facilitate the development of differentiation therapy as a viable clinical tool.